How to validate email id in angularJs using ng-pattern

If you want to validate email then use input with type="email" instead of type="text". AngularJS has email validation out of the box, so no need to use ng-pattern for this.

Here is the example from original documentation:

<script>
function Ctrl($scope) {
  $scope.text = '[email protected]';
}
</script>
<form name="myForm" ng-controller="Ctrl">
  Email: <input type="email" name="input" ng-model="text" required>
  <br/>
  <span class="error" ng-show="myForm.input.$error.required">
    Required!</span>
  <span class="error" ng-show="myForm.input.$error.email">
    Not valid email!</span>
  <br>
  <tt>text = {{text}}</tt><br/>
  <tt>myForm.input.$valid = {{myForm.input.$valid}}</tt><br/>
  <tt>myForm.input.$error = {{myForm.input.$error}}</tt><br/>
  <tt>myForm.$valid = {{myForm.$valid}}</tt><br/>
  <tt>myForm.$error.required = {{!!myForm.$error.required}}</tt><br/>
  <tt>myForm.$error.email = {{!!myForm.$error.email}}</tt><br/>
</form>

For more details read this doc: https://docs.angularjs.org/api/ng/input/input%5Bemail%5D

Live example: http://plnkr.co/edit/T2X02OhKSLBHskdS2uIM?p=info

UPD:

If you are not satisfied with built-in email validator and you want to use your custom RegExp pattern validation then ng-pattern directive can be applied and according to the documentation the error message can be displayed like this:

The validator sets the pattern error key if the ngModel.$viewValue does not match a RegExp

<script>
function Ctrl($scope) {
  $scope.text = '[email protected]';
  $scope.emailFormat = /^[a-z]+[a-z0-9._]+@[a-z]+\.[a-z.]{2,5}$/;
}
</script>
<form name="myForm" ng-controller="Ctrl">
  Email: <input type="email" name="input" ng-model="text" ng-pattern="emailFormat" required>
  <br/><br/>
  <span class="error" ng-show="myForm.input.$error.required">
    Required!
  </span><br/>
  <span class="error" ng-show="myForm.input.$error.pattern">
    Not valid email!
  </span>
  <br><br>
  <tt>text = {{text}}</tt><br/>
  <tt>myForm.input.$valid = {{myForm.input.$valid}}</tt><br/>
  <tt>myForm.input.$error = {{myForm.input.$error}}</tt><br/>
  <tt>myForm.$valid = {{myForm.$valid}}</tt><br/>
  <tt>myForm.$error.required = {{!!myForm.$error.required}}</tt><br/>
  <tt>myForm.$error.pattern = {{!!myForm.$error.pattern}}</tt><br/>
</form>

Plunker: https://plnkr.co/edit/e4imaxX6rTF6jfWbp7mQ?p=preview

According to the answer of @scx ,I created a validation for GUI

app.directive('validateEmail', function() {
  var EMAIL_REGEXP = /^[_a-z0-9]+(\.[_a-z0-9]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/;
  return {
    link: function(scope, elm) {
      elm.on("keyup",function(){
            var isMatchRegex = EMAIL_REGEXP.test(elm.val());
            if( isMatchRegex&& elm.hasClass('warning') || elm.val() == ''){
              elm.removeClass('warning');
            }else if(isMatchRegex == false && !elm.hasClass('warning')){
              elm.addClass('warning');
            }
      });
    }
  }
});

And simply add :

css

.warning{
   border:1px solid red;
 }

html

<input type='email' validate-email name='email' id='email' ng-model='email' required>

There is nice example how to deal with this kind of problem modyfing built-in validators angulardocs. I have only added more strict validation pattern.

app.directive('validateEmail', function() {
  var EMAIL_REGEXP = /^[_a-z0-9]+(\.[_a-z0-9]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/;

  return {
    require: 'ngModel',
    restrict: '',
    link: function(scope, elm, attrs, ctrl) {
      // only apply the validator if ngModel is present and Angular has added the email validator
      if (ctrl && ctrl.$validators.email) {

        // this will overwrite the default Angular email validator
        ctrl.$validators.email = function(modelValue) {
          return ctrl.$isEmpty(modelValue) || EMAIL_REGEXP.test(modelValue);
        };
      }
    }
  };
});

And simply add

<input type='email' validate-email name='email' id='email' ng-model='email' required>